The present invention relates to an apparatus and method for applying an electrical bias potential to one or more workpieces/substrates carried by a moving pallet past at least one workpiece/substrate treating station, without incurring deleterious electrical arcing between the pallet and a bias rail utilized for applying the bias potential to the pallet. The invention has particular utility in the automated manufacture of magnetic or magneto-optical (MO) recording media comprising a multi-layer stack of thin film layers formed on a suitable substrate, e.g., a disk-shaped substrate, by means of a physical vapor deposition process, e.g., sputtering.
Magnetic and MO media are widely employed in various applications, particularly in the computer industry for data/information storage and retrieval purposes. A magnetic medium in e.g., disk form, such as utilized in computer related applications, comprises a non-magnetic substrate, e.g., of glass, ceramic, glass-ceramic composite, polymer, metal, or metal alloy, typically an aluminum (Al)-based alloy such as aluminum-magnesium (Al-Mg), having at least one major surface on which a layer stack comprising a plurality of thin film layers constituting the medium are sequentially deposited. Such layers may include, in sequence from the workpiece (substrate) deposition surface, a plating layer, e.g., of amorphous nickel-phosphorus (Nlxe2x80x94P), a polycrystalline underlayer, typically of chromium (Cr) or a Cr-based alloy such as chromium-vanadium (Crxe2x80x94V), a magnetic layer, e.g., of a cobalt (Co)-based alloy, and a protective overcoat layer, typically of a carbon-based material having good mechanical (i.e., tribological) properties. A similar situation exists with MO media, wherein a layer stack is formed which comprises a reflective layer, typically of a metal or metal alloy, one or more rare-earth thermo-magnetic (RExe2x80x94TM) alloy layers, one or more dielectric layers, and a protective overcoat layer, for functioning as reflective, transparent, writing, writing assist, read-out, and protective layers.
According to conventional manufacturing methodology, a majority of the above-described layers constituting magnetic and/or MO recording media are deposited by cathode sputtering, typically by means of multi-cathode and/or multi-chamber sputtering apparatus wherein a separate cathode comprising a selected target material is provided for deposition of each component layer of the stack and the sputtering conditions are optimized for the particular component layer to be deposited. Each cathode comprising a selected target material can be positioned within a separate, independent process chamber, in a respective process chamber located within a larger chamber, or in one of a plurality of separate, interconnected process chambers each dedicated for deposition of a particular layer. According to such conventional manufacturing technology, a plurality of media substrates, typically in disk form, are serially transported by means of a multi-apertured pallet or similar type holder, in linear or circular fashion, depending upon the physical configuration of the particular apparatus utilized, from one sputtering target and/or process chamber to another for sputter deposition of a selected layer thereon.
Cost-effective productivity requirements imposed by automated manufacturing technology for magnetic and MO media require maximized sputter deposition rates, while at the same time, high quality, high areal recording density media require high purity thin film layers which exhibit respective physical, chemical, and/or mechanical properties, including, inter alia, proper crystal morphology necessary for obtaining high areal recording densities, e.g., polycrystallinity; good magnetic properties, e.g., coercivity and squareness ratio; chemical stability, e.g., inertness or corrosion resistance; and good tribological properties, e.g., wear resistance and low stiction/friction. Frequently, obtainment of such desirable physical, chemical, and/or mechanical properties for each of the constituent layers of the multi-layer media requires application of an electrical bias potential to the substrate during sputtering, e.g., a DC, AC, or RF bias potential, or some combination thereof, wherein the bias type and level of bias potential is optimized for each constituent layer
For example, application of a suitable substrate bias during sputter deposition of metal-based underlayers and ferromagnetic metal alloy layers of thin film magnetic recording media can facilitate obtainment of preferred crystal orientations. In addition, application of a suitable bias during deposition of carbon (C)-based protective overcoat layers, e.g., diamond-like carbon (DLC) films, on thin film magnetic and MO recording media is extremely useful in increasing the density thereof to yield thinner films necessary for achieving ultra-high recording densities, while maintaining good tribological and corrosion resistance attributes of DLC films. For example, application of a negative electrical bias during DLC deposition in an argon (Ar)/hydrocarbon plasma causes positive ions, such as Ar+ and C2H0+ ions, to bombard the depositing DLC film, thereby compacting and densifying the film.
Referring to FIGS. 1-2, shown therein, in simplified, schematic cross-sectional top and side views, respectively, is an illustrative, but not limitative, embodiment of an in-line, pass-by apparatus for treating opposing surfaces of a plurality of vertically mounted workpieces/substrates (as disclosed in co-pending, commonly assigned U.S. application Ser. No. 10/212,693 filed Aug. 7, 2002), which apparatus can, if desired, form part of a larger, in-line apparatus for continuous, automated manufacture of, e.g., magnetic and/or magneto-optical (MO) recording media such as hard disks, and wherein a plurality of vertically oriented workpieces/substrates (e.g., disks) are transported in a linear path transversely past at least one treatment station for treatment of at least one surface of each of the plurality of workpieces/substrates.
More specifically, apparatus 10 comprises a series of linearly elongated vacuum chambers interconnected by a plurality of gate means G of conventional design, including a plurality of treatment chambers or stations, illustratively a pair of treatment chambers or stations 1 and 1xe2x80x2, each including at least one, preferably a pair of spaced-apart, oppositely facing, linearly elongated treatment sources 2, 2xe2x80x2, selected from among a variety of physical vapor deposition (PVD) sources, such as vacuum evaporation, sputtering, ion beam deposition (IBD), ion plating, plasma-enhanced chemical vapor deposition (PECVD), etc., sources, and/or from among a variety of plasma treatment sources, such as sputter/ion etching, hydrogen, nitrogen, oxygen, argon, etc., plasma sources for performing simultaneous treatment of both sides of dual-sided workpieces/substrates, and a pair of buffer/isolation chambers, such as 3, 3xe2x80x2 and 3xe2x80x2, 3xe2x80x3, at opposite lateral ends of respective treatment chambers or stations 1 and 1xe2x80x2 for insertion and withdrawal, respectively, of a plurality of vertically oriented workpieces/substrates, illustratively a plurality disk-shaped substrates 4 carried by a plurality of workpiece/substrate mounting/transport means, illustratively means 5, 5xe2x80x2, which may, for example, be in the form of a perforated, flat planar pallet including conventional means (not shown in the drawing for illustrative simplicity) for releasable mounting/supporting the plurality of disk-shaped substrates 4 such that each of the opposing surfaces thereof faces a respective linearly elongated treatment source 2, 2xe2x80x2 during xe2x80x9cpass-byxe2x80x9d transport through apparatus 10. Chambers 6, 6xe2x80x2 respectively connected to the distal ends of inlet and outlet buffer/isolation chambers 3, 3xe2x80x3 are provided for utilizing apparatus 10 as part of a larger, continuously operating, in-line apparatus wherein workpieces/substrates 4 receive processing/treatment antecedent and/or subsequent to processing in apparatus 10.
Apparatus 10 is, if required by the nature/mode of operation of treatment sources 2, 2xe2x80x2, provided with conventional vacuum means (not shown in the drawing for illustrative simplicity) for maintaining the interior spaces of each of the constituent chambers 1, 1xe2x80x2, 3, 3xe2x80x2, 3xe2x80x3, etc. at a reduced pressure below atmospheric pressure, e.g., from about 10xe2x88x925 to about 10xe2x88x929 Torr, and is further provided with a workpiece/substrate conveyor/transporter means of conventional design (not shown in the drawings for illustrative simplicity) for linearly transporting the workpiece/substrate mounting means 5, 5xe2x80x2 through the respective gate means G from chamber-to-chamber in its travel through apparatus 10.
As indicated above, when utilized in the manufacture of disk-shaped magnetic and/or MO recording media, the workpieces/substrates 4, 4xe2x80x2 carried by mounting means 5, 5xe2x80x2 are in the form of annular discs, with inner and outer diameters corresponding to those of conventional hard disc-type magnetic and/or MO media, and each of the illustrated treatment chambers 1, 1xe2x80x2 of apparatus 10 is provided with a pair of opposingly facing, linearly extending physical vapor deposition sources 2, typically elongated magnetron sputtering sources, for deposition of respective constituent thin films of the multi-layer magnetic or MO media on each surface of each of the plurality of disks 4, 4xe2x80x2 carried by the perforated pallet-type mounting means 5, 5xe2x80x2.
The pallet-type mounting means 5, Sxe2x80x2 for mounting/transporting a plurality of disk-shaped workpieces/substrates 4, 4xe2x80x2, respectively, may be generally similar to that shown and disclosed in U.S. Pat. No. 5,814,196 to Hollars, et al., the entire disclosure of which is incorporated herein. Adverting to FIG. 3, shown therein is a simplified, schematic side view of a pallet 5 adapted for mounting and transporting a plurality of vertically oriented, disk-shaped workpieces/substrates 4, e.g., for use in the in-line apparatus 10 of FIGS. 1-2 for depositing a plurality of thin film layers constituting a multi-layer thin film stack or laminate of a magnetic or MO recording medium. Pallet 5 typically comprises a sheet 5S of an electrically conductive material, e.g., Al or an Al-alloy, machined to include a plurality of generally circularly-shaped apertures 7 extending therethrough, each aperture 7 including a semi-circularly extending groove formed in the lower half of the interior wall thereof for insertion and secure mounting of respective disk-shaped workpieces/substrates 4 therein, as is more fully described in the above-mentioned Hollars et al. U.S. Pat. No. 5,814,196. Pallet 5 further includes a pair of holes 8 extending through sheet 5S at the top edge thereof for attachment to a linear transport mechanism (of conventional design not described herein for brevity) of apparatus 10 for moving pallet 5 through each of the serially arranged isolation and treatment (e.g., deposition) chambers, gates, air locks, etc., and a plurality of slots 9 extending through sheet 5S at various locations about the periphery thereof for providing stress relief and thermal isolation during passage through apparatus 10, also as described more fully in U.S. Pat. No. 5,814,196. Contact bar 11 is provided at the lower edge of sheet 5S for making sliding electrical contact with a conductive rail 12 (refer to FIGS. 1-2) located at the bottom of one or more of the treatment chambers/stations 1, 1xe2x80x2, etc., for application of a suitable DC, AC, or RF bias potential (or any combination thereof) to sheet 5S, as by means of one or more bias potential sources electrically connected to one or more bias rail segments 12 (which one or more sources are not shown in FIGS. 1-2 for illustrative simplicity).
However, conventional bias rails, such as bias rail segments 12, are entirely metallic (hence electrically conductive) and of relatively large size, and as a consequence, during use, e.g., for depositing a DLC protective overcoat layer during the manufacture of magnetic or MO recording media, a dielectric coating comprised of DLC is formed thereon after exposure of the rail segment(s) 12 for an interval to a gas plasma utilized for the DLC deposition. Formation of the dielectric DLC coating layer on the bias rail segments disadvantageously results in arcing during the DLC deposition, which arcing is deleterious in that particles generated by the arcing cause glide rejects or voids in the DLC protective overcoat layers of the magnetic disks, thereby adversely affecting both product quality and yield. In extreme situations, arcing may necessitate shut-down of the production line in order to avoid loss of product quality and yield, which shutdown is extremely uneconomic in large scale manufacturing processing. For example, the cost (or value of product) of operating a typical large-scale apparatus for the automated manufacture of hard disks may be as high as about $ 25 K/hour; hence a shut-down time of about 30 min. due to arcing problems may incur an economic loss of as high as about $ 12.5 K.
Arcing typically occurs during switchover of the pallet from an unbiassed state to a biassed state, and may persist for about 30-40 min., or as long as is required for the energized bias rail surface to become free of the dielectric DLC coating layer. Arcing may still occur sporadically during subsequent operation because of the continued exposure of the bias rail segment(s) to the deposition plasma.
A further problem associated with the conventional bias rails arises from coupling of plasmas in adjacent deposition/treatment chambers. In such instances, the large area of the electrically conductive bias rail serves as the power electrode and the chamber walls serve as the ground electrode. The coupling plasma in the leading (i.e., upstream) chamber generates small particles (dust) which tend to settle on the clean surfaces of the disk workpieces/substrates prior to deposition of the first stratum of the DLC film. The presence or inclusion of such dust particles below or within the DLC film disadvantageously leads to glide rejects, voids in the DLC films, and poor film adhesion. Similarly, coupling plasma present in the trailing (i.e., downstream) chamber also results in contamination of the workpicce/substrate surface prior to deposition thereon.
In view of the foregoing, there exists a clear need for improved means and methodology for treating workpieces/substrates carried by a moving workpiece/substrate holder past one or more treatment stations of an apparatus where an electrical bias potential is applied to the workpieces/substrates, which improved means and methodology do not incur the problems, disadvantages, and drawbacks associated with the use of conventionally configured bias rails for supplying the workpieces/substrates with the electrical bias potentials. More specifically, the present invention provides means and methodology for performing pass-by treatment of workpieces/substrates in a series of processing stations without incurring deleterious arcing between the workpiece/substrate carrier (e.g., pallet) and the bias rail, and/or without incurring plasma coupling between upstream and downstream processing chambers, and is of particular utility in the automated manufacture of thin film magnetic and/or magneto-optical (MO) recording media involving seriatim deposition of a plurality of thin film layers in plasma environments. Further, the inventive means and methodology afford full compatibility with all aspects of conventional automated manufacturing technology for such media and enjoy diverse utility in the manufacture of various devices and articles requiring the formation of high quality, defect-free thin films with optimal physical, chemical, and/or mechanical properties.
An advantage of the present invention is an improved non-arcing bias rail assembly for electrically contacting and supplying an electrical bias potential to a moving workpiece/substrate holder.
Another advantage of the present invention is an improved apparatus for performing a plurality of treatments of at least one surface of each of a plurality of workpieces/substrates.
Yet another advantage of the present invention is an improved apparatus for performing bias sputter deposition on a plurality of moving workpieces/substrates.
A further advantage of the present invention is an improved method of processing/treating at least one surface of each of a plurality of moving workpieces/substrates.
A still further advantage of the present invention is an improved method of performing bias sputter treatment of at least one surface of each of a plurality workpieces/substrates.
Additional advantages and other features of the present invention will be set forth in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from the practice of the present invention. The advantages of the present invention may be realized and obtained as particularly pointed out in the appended claims.
According to an aspect of the present invention, the foregoing and other advantages are obtained in part by a non-arcing bias rail assembly for electrically contacting and supplying an electrical bias potential to a workpiece/substrate holder, comprising:
(a) a flat, elongated metal strip with a major surface bounded by first and second opposed, laterally extending side edges, the strip being adapted for mounting along a wall of a chamber of a workpiece/substrate treatment apparatus;
(b) a first bracket comprised of an electrically insulating material, the first bracket:
(i) including a first portion parallel to and mounted on the major surface of the metal strip adjacent the first side edge thereof;
(ii) extending along a portion of the first side edge; and
(iii) including a second portion forming an upstanding wall extending perpendicularly from the first portion, the upstanding wall including a surface facing the second side edge of the metal strip;
(c) a first electrically conductive bias contact spring assembly, the first bias contact spring assembly mounted on the surface of the upstanding wall of the first bracket facing the second side edge of the metal strip; and
(d) first electrically insulated wire means electrically connected to the first bias contact spring assembly for supplying the first bias contact spring assembly with an electrical bias potential.
According to embodiments of the present invention, the bias rail assembly further comprises:
(e) a second bracket comprised of an electrically insulating material, the second bracket:
(i) including a first portion parallel to and mounted on the major surface of the metal strip adjacent the second side edge thereof;
(ii) extending along a portion of the second side edge; and
(iii) including a second portion forming an upstanding wall extending perpendicularly from the first portion, the upstanding wall including a surface facing the first side edge of the metal strip;
(f) a second electrically conductive bias contact spring assembly, the second bias contact spring assembly mounted on the surface of the upstanding wall of the second bracket facing the first side edge of the metal strip; and
(g) second electrically insulated wire means electrically connected to the second bias contact spring assembly for supplying the second bias contact spring assembly with an electrical bias potential; wherein:
each of the first and second brackets comprises a ceramic material or ceramic-coated metal and each of the first and second electrically conductive bias contact spring assemblies is generally arcuately-shaped.
In accordance with further embodiments of the present invention, each of the first and second electrically conductive bias contact spring assemblies comprises an inner electrically conductive spring and an outer electrically conductive contact spring, whereas, according to other embodiments of the invention, each of the first and second electrically conductive bias contact spring assemblies comprises, in sequence, an electrically insulative inner spring, an electrically conductive bias contact spring including a centrally located protruding portion, and an electrically insulative outer spring including a centrally located opening for accommodating therein and exposing the centrally located protruding portion of the bias contact spring, wherein each of the electrically insulative inner and outer springs comprises a ceramic material or ceramic-coated metal.
According to still other embodiments of the present invention, each of the first and second electrically conductive bias contact spring assemblies comprises, in sequence, an electrically insulative inner spring, an electrically conductive bias contact spring, an electrically insulative outer spring including a centrally located opening, and an electrical contact means exposed and positioned within the centrally located opening of the electrically insulative outer spring bias contact spring and electrically connected to the electrically conductive bias contact spring, wherein each of the electrically insulative inner and outer springs comprises a ceramic material or ceramic-coated metal, and the electrical contact means comprises a pair of tabs extending through a pair of openings in the electrically conductive bias contact spring.
Embodiments according to the present invention include those which further comprise:
(h) at least one pair of guide means mounted to the elongated metal strip and adapted for guiding first and second oppositely facing surfaces of the moving workpiece/substrate holder into respective electrical contact with the first and second electrically conductive bias contact spring assemblies, wherein each of the guide means is electrically insulated for preventing arcing, e.g., each of the guide means comprises a ceramic cap.
According to additional embodiments of the present invention, the elongated metal strip includes at least one centrally located, laterally extending opening permitting movement of particulate material therethrough.
Another aspect of the present invention is an apparatus for performing a plurality of treatments of at least one surface of each of a plurality of moving workpieces/substrates, comprising:
(a) a plurality of linearly spaced-apart treatment stations for performing a corresponding plurality of treatments of at least one surface of each of the workpieces/substrates;
(b) a pallet adapted for mounting the plurality of workpieces/substrates and exposing the at least one surface of each of the workpieces/substrates for receipt of the plurality of treatments, the pallet including first and second contact strips on opposite sides thereof for making electrical contact with at least one bias potential source of the apparatus;
(c) means for transporting the pallet past the plurality of treatment stations;
wherein at least one of the plurality of treatment stations includes:
(d) means for applying an electrical bias potential to the plurality of workpieces/substrates, including a non-arcing bias rail assembly for making sliding electrical contact with the contact strip of the pallet, comprising:
(i) a flat, elongated metal strip mounted on an interior wall of the at least one treatment station, the strip having a major surface bounded by first and second opposed, laterally extending side edges;
(ii) a first bracket comprised of an electrically insulating material, the first bracket:
(1) including a first portion parallel to and mounted on the major surface of the metal strip adjacent the first side edge thereof;
(2) extending along a portion of the first side edge; and
(3) including a second portion forming an upstanding wall extending perpendicularly from the first portion, the upstanding wall including a surface facing the second side edge of the metal strip;
(iii) a first electrically conductive bias contact spring assembly for electrically contacting the first contact strip of the pallet, the first bias contact spring assembly mounted on the surface of the upstanding wall of the first bracket facing the second side edge of the metal strip; and
(iv) first electrically insulated wire means electrically connected to the first bias contact spring assembly for supplying the first bias contact spring assembly with an electrical bias potential.
According to embodiments of the present invention, the means for applying an electrical bias potential to the moving workpieces/substrates further comprises:
(v) a second bracket comprised of an electrically insulating material, the second bracket:
(1) including a first portion parallel to and mounted on the major surface of the metal strip adjacent the second side edge thereof;
(2) extending along a portion of the second side edge; and
(3) including a second portion forming an upstanding wall extending perpendicularly from the first portion, the upstanding wall including a surface facing the first side edge of the metal strip;
(vi) a second electrically conductive bias contact spring assembly for electrically contacting the second contact strip of the pallet, the second bias contact spring assembly mounted on the surface of the upstanding wall of the second bracket facing the first side edge of the metal strip; and
(vii) second electrically insulated wire means electrically connected to the second bias contact spring assembly for supplying the second bias contact spring assembly with an electrical bias potential.
Embodiments of the present invention include those wherein the plurality of treatment stations are selected from among physical vapor deposition (PVD) stations and plasma treatment stations. According to preferred embodiments of the present invention, the PVD stations arc bias sputter deposition stations.
Yet another aspect of the present invention is a method of processing/treating at least one surface of each of a plurality of moving workpieces/substrates, comprising steps of:
(a) mounting a plurality of workpieces/substrates on a pallet such that at least one surface of each of the plurality of workpieces/substratcs is exposed for processing/treatment, the pallet including first and second contact strips on opposite sides thereof;
(b) processing/treating the at least one surface of each of the plurality of workpieces/substrates at each of a plurality of processing/treating stations of an in-line processing/treating apparatus, the processing/treating comprising:
(i) transporting the pallet successively through each of the processing/treating stations; and
(ii) applying a pre-selected electrical bias potential to at least one surface of each of the plurality of workpieces/substrates during processing/treatment thereof in at least one of said plurality of processing/treating stations by means of a non-arcing bias rail assembly making sliding electrical contact with a first contact strip on a first side of the pallet, comprising:
(1) a flat, elongated metal strip mounted on an interior wall of the at least one treatment station, the strip having a major surface bounded by first and second opposed, laterally extending side edges;
(2) a first bracket comprised of an electrically insulating material, the first bracket:
including a first portion parallel to and mounted on the major surface of the metal strip adjacent the first side edge thereof;
extending along a portion of the first side edge; and
including a second portion forming an upstanding wall extending perpendicularly from the first portion, the upstanding wall including a surface facing the second side edge of the metal strip);
(3) a first electrically conductive bias contact spring assembly for electrically contacting the first contact strip of the pallet, the first bias contact spring assembly mounted on the surface of the upstanding wall of the first bracket facing the second side edge of the metal strip; and
(4) first electrically insulated wire means electrically connected to the first bias contact spring assembly for supplying the first bias contact spring assembly with an electrical bias potential.
According to embodiments of the present invention, step (b) further comprises applying an electrical bias potential to both surfaces of each of the plurality of moving workpieces/substrates during processing/treatment thereof in at least one of the plurality of processing/treating stations by means of a non-arcing bias rail assembly making sliding electrical contact with a second contact strip on the second side of the pallet, comprising:
(1) a second bracket comprised of an electrically insulating material, the second bracket:
including a first portion parallel to and mounted on the major surface of the metal strip adjacent the second side edge thereof;
extending along a portion of the second side edge; and
including a second portion forming an upstanding wall extending perpendicularly from the first portion, the upstanding wall including a surface facing the first side edge of the metal strip;
(2) a second electrically conductive bias contact spring assembly for electrically contacting the second contact strip on the second side of the pallet, the second bias contact spring assembly mounted on the surface of the upstanding wall of the second bracket facing the first side edge of the metal strip; and
(3) second electrically insulated wire means electrically connected to the second bias contact spring assembly for supplying the second bias contact spring assembly with an electrical bias potential.
According to preferred embodiments of the present invention, processing/treating step (b) comprises bias sputtering.
Additional advantages and aspects of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein embodiments of the present invention are shown and described, simply by way of illustration of the best mode contemplated for practicing the present invention. As will be described, the present invention is capable of other and different embodiments, and its several details are susceptible of modification in various obvious respects, all without departing from the spirit of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as limitative.